In mice transgenic for the R4A gamma2b heavy chain of an anti-double stranded (ds) DNA antibody, the transgenic heavy chain can pair with a variety of endogenous light chains to produce anti-dsDNA antibodies of different affinities and fine specificities. We have demonstrated that B-cells producing high affinity transgenic anti-dsDNA antibodies are regulated by anergy and deletion in non-autoimmune transgenic mice, whereas in the NZB/W F1 mouse strain, high affinity transgene encoded anti-dsDNA antibody is present in the serum. B-cell hybridomas have been generated from spleen and bone marrow cells of non-autoimmune and autoimmune transgenic mice. Initial results suggest that there are three subsets of transgenic anti-dsDNA secreting B-cells. One subset secretes a high affinity anti-dsDNA antibody that utilizes a Vk1 light chain and is targeted for anergy. These B-cells display a lack of allelic exclusion. Another subset secretes high affinity anti-dsDNA antibody encoded by non Vk1 light chains. These are targeted for deletion. A third subset secretes low affinity anti-dsDNA antibodies which escape regulation. These cells display intact allelic exclusion. We would like to confirm these results by obtaining additional hybridomas from bone marrow and spleen cells derived from non autoimmune transgenic mice. We would also like to determine why these populations of B-cells are regulated differently and we propose to identify affinity and fine specificity differences among these subsets. We will see if bcl-2 can rescue one or both of the subsets of B-cells secreting high affinity anti-dsDNA antibody. We recently generated mice transgenic for the R4Amu heavy chain transgene. We would like to compare the regulation of B-cells secreting transgenic IgM anti-dsDNA antibody with those secreting transgenic IgG2b anti-dsDNA antibody to determine if signaling mechanisms affecting tolerance induction differ between these two isotypes.